用所给词的适当形式填空。

1. Please ___ (not) run in the classroom. 　　

2. I'm ___ (eat) some bananas. 　　

3. She often goes ___ (shop) with her mother on Sunday. 　　

4. Please ___ (not play) in the street. 　　

5. The boy is too young ___ (go) to school. 　　

6. Which is ___ (fast), a train or a plane. 　　

7. This shirt is ___ (cheap) than your shirt.

叶轮中有污泥杂草堵塞会造成轴流泵（）。

A.流量不足

B.发热

C.振动

D.不出水